Covers currently used with more than 90 percent of all spas and hot tubs that are covered during nonuse include a closed cell foam plastic core covered with vinyl plastic cloth. Frequently aluminum channel or plywood is included to increase strength. The main advantage of present covers is the reduction in heat loss due to the good insulating properties of closed cell foam. Correctly fitted, new covers look neat and prevent debris from entering the spa.
The major disadvantage of contemporary spa covers of the type described above is the significant weight that such covers gain as a result of water absorption. More specifically, even the best closed cell foams absorb spa condensation over time. increasing the weight of a closed cell foam spa cover. The weight may double and triple in only a couple of years. Two- to three-year-old covers are commonly so heavy that the average person has difficulty lifting them. Unfortunately, the water stored in a closed cell foam spa cover cannot be purged. It is permanently retained by the foam. While lift mechanisms have been developed for assisting in the installation and removal of spa covers, such mechanisms are cumbersome and are not practical in many installations.
Another disadvantage of foam core spa covers is their propensity to crack or break when subjected to the weight of an adult standing on the center of a cover installed on a spa. This disadvantage is particularly true with respect to original equipment spa covers. i.e.. those supplied when a spa is installed. Such covers are often of low quality and cost. While replacement market spa covers are of higher quality, price quickly escalates with strength and durability, and the installation of lifting mechanisms.
Because foam core spa covers typically only fold to half their full size, storage is very difficult. The bulky nature of foam core makes foam core spa covers expensive to ship to and store by distributors. These problems prevent any manufacturer without regional manufacturing capability from becoming a national supplier.
A further disadvantage of foam core spa covers is the difficulty in locking them to a spa. Because locking a foam core spa cover is typically cumbersome and impractical, it is seldom done. This allows unauthorized people to have ready access to spas covered by foam core spa covers.
Prior attempts to overcome the foregoing disadvantages of foam core spa covers have involved rigid dome-shaped covers, flexible floating covers and flexible covers supported by air-inflated bags and the like. All of these covers have disadvantages. Rigid dome covers (see U.S. Pat. No. 4,426,663) are complex. Flexible floating covers (see U.S. Pat. No. 4,109,325) are somewhat difficult to store. More importantly, floating covers do not provide support for an adult or limit access to a spa. Flexible covers supported by air-inflated bags and the like require a separate inflation source, often do not limit access to a spa and/or are more difficult to store than desired. See U.S. Pat. Nos. 3,366,977; 3,608,099; 3,747,131; 3,801,994: 4,048,678; 4,606,083; 4,825,479; 4,847,925 and 4,953,239.
Hence, a need exists for a spa cover which is simple to use, can be folded for storage, lightweight (less than 20 lbs. for an average spa), does not increase in weight over time, supports the weight of an adult, deters unwanted entry and keeps debris out while providing good, thermal insulation. The present invention is directed to providing such a spa cover.